Michigan State University Extension
Ornamental Plants plus Version 3.0 - 00001645
11/12/99

Salt


Salt spray causes brown foliage on evergreens or
"witches'-broom" on deciduous plants. A witches'-broom is
a cluster of twigs that forms on a branch. Prolonged
exposure to salt spray can lead to dieback.

Salt spray can drift to plants from nearby roads as the
tires of passing cars kick up a salty spray. The water
evaporates, leaving a salt residue. Short plants can be
protected from the spray with tar-backed burlap screens.
Larger plants can not be protected. Road salt can also be
a problem when salty run-off accumulates salt in the root
zones of plants growing near the road.

Salt can injure landscape plants when salt used on porches
and sidewalks is shoveled or swept onto nearby shrubs,
where it accumulates on the foliage or in the root zones.
Most chemical deicers will have the same injurious
effects, though calcium chloride is not as harmful as
sodium chloride. Fertilizer is sometimes used, but it,
too, can build up to toxic levels. Sand and ashes are not
toxic but have the disadvantage of being easily tracked
into the house.

A third source of salt can be softened water running into
septic systems. Evergreens will display browned foliage
that forms a rough spiral as it moves up the tree. Trees
may grow well for a number of years and then show symptoms
when their roots finally reach the source of the salt.

Tree species vary in their susceptibility to salt injury.
A susceptible species such as white pine should not be
planted near roadsides where salt will be applied.


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